Do you mean a box which can run Gentoo or a box which comes with Gentoo preinstalled? If the latter, then I doubt it.

I'm looking for two, one to run as my webserver and one that would be fully HD video capable device that network and attach to my media/tv centre. Possibly a third to replace my desktop as I don't use it much anymore.

My reason is that I've got to hooking huge workstation and a server that are under used and consume gross amount of electricity, I'd looking to reduce my energy consumption to something that does not make me wince.

If you require media playback capabilities and not so much storage, an option would be Zotac ZBOX or ZBOX Nano. They come in Intel or AMD variants, and support accelerated video decode with open source drivers (radeon needs patched kernel and mesa-9.2). Prices start around 200 USD without RAM and hard disk. They are also suitable for light desktop use.

In case storage is required, then a HP MicroServer might be good. You would however have to install a low-profile graphics card if you need HDMI out. You are looking at 30-40W power consumption depending on the number of hard disks that you install.

If that is still to high and you are looking at <10W devices:
An option would be one of the ARM based Android TV dongles like the MK802 II. You can easily replace Android with another Linux distro. Another low-power alternative could be a Seagate FreeAgent GoFlex which can run a webserver and network shares but not much more.

The ARM based developer boards like Raspberry Pi, Cubieboard, Odroid, OLinuXino etc. are worth looking at if you want to tinker with home automation, connecting touch screens or similar.